High current capacity single-pole electrical connectors have tended to be difficult to assemble and cumbersome in use, particularly where connecting and disconnecting must be frequently accomplished.
Currently available on the market is a widely used, high-power, single-pole connector plug and receptacle connector set identified as the Cam-Lok.RTM., E-Series. This connector set has been in use for over fifty years and is sold by the Crouse-Hinds Division of Cooper Industries. The receptacle is used with a mating straight plug. Both the receptacle and the plug of the Cam-Lok.RTM., E-Series connector set are rubber sheathed for purposes of environmental sealing, electrical insulation for operator safety, and to provide a good gripping surface for manual connection and disconnection. The Cam-Lok.RTM., E-Series receptacle includes a non-conductive, plate-like mounting base which appears square in plan view, a non-conductive, substantially cylindrical sleeve extending integrally from the mounting base, and a conductive contact pin positioned coaxially within the sleeve and usually having a threaded shank extending out of the unit on the side opposite the sleeve. Openings are provided adjacent the corners of the mounting base, to allow passage of fasteners such as bolts, rivets, etc. for fastening the receptacle to a mounting surface.
The leading end of the mating straight plug of the Cam-Lok.RTM., E-Series connector set typically has a forwardly converging, conical configuration. This allows it to fit inside the cylindrical sleeve of the receptacle and achieve a slight pressure fit which provides a moisture seal. Within the conical leading end of the conventional plug is the end of an electrically conductive contact member which is cylindrical in configuration, with an axial opening adapted to snugly receive the contact pin within the receptacle sleeve. (This assumes the receptacle is the "hot" side of the circuit (source) and the plug is the cold side (drain). However, the gender can be reversed with a different plug and receptacle combination). This electrical contact involves geometries (explained below) which provide a cam action to achieve a secure, low resistance electrical connection. Although the rubber sheaths of the plugs are color-coded to identify ground, neutral, and three electrical phases, this conventional design contains no provision to prevent inadvertent cross-plugging of connectors, that is for example, plugging a phase cable into a neutral or ground connector.
In the conventional Cam-Lok.RTM., E-Series construction, the cable is attached to the contact member on the plug side by way of set screws. The Cam-Lok.RTM. design also typically uses an internal wire to grip the jacket of the cable for providing strain relief.